Other ECPs

There are several issues to consider when using ECP basis sets. The core potential may represent all but the outermost electrons. In other ECP sets, the outermost electrons and the last filled shell will be in the valence orbital space. Having more electrons in the core will speed the calculation, but results are more accurate if the —1 shell is outside of the core potential. Some ECP sets are designated as shape-consistent sets, which means that the shape of the atomic orbitals in the valence region matches that for all electron basis sets. ECP sets are usually named with an acronym that stands for the authors names or the location where it was developed. Some common core potential basis sets are listed below. The number of primitives given are those describing the valence region. 

Electronically conducting polymers (ECPs) such as polyaniline (PANI), polypyrrole (PPy) and po 1 y(3.4-cthy 1 cncdi oxyth iophcnc) (PEDOT) have been applied in supercapacitors, due to their excellent electrochemical properties and lower cost than other ECPs. We demonstrated that multi-walled carbon nanotubes (CNTs) prepared by catalytic decomposition of acetylene in a solid solution are very effective conductivity additives in composite materials based on ECPs. In this paper, we show that a successful application of ECPs in supercapacitor technologies could be possible only in an asymmetric configuration, i.e. with electrodes of different nature. 

The performance of the P3 method used in conjunction with ECPs is also encouraging. Among the p group metals, the CEP-4G set is the most accurate (MAD of 0.67 eV), with the SHC potential of Goddard and Smedley performing best for the alkalis and alkaline earths (MAD of 0.34 eV). The SDD sets succeed in all three cases and produce errors that are competitive with all of the other ECPs. 

This overview of the ECP derivation process highlights some issues that arise in derivation of the potentials and their attendant valence basis sets. Lanthanides are used to illustrate the process. The discussion is based on the derivation of lanthanide ECPs and valence basis sets described by Cundari and Stevens3= which follows the same scheme used by Stevens et al. in their ECP implementation for the transition metals, and is similar to the processes used by other ECP researchers.3- The ECP derivation process is depicted schematically in Chart 1. Differences are noted where appropriate. Szasz has reviewed some of the earlier ECP derivation processes. ... 

The application of conjugated polymer films as gas separation membranes has also been described [195-197]. The ability of ECPs to separate mbrtures of gases was related to differences in permeabilities of gases through the polymer films. Provided that the morphology and the porosity of this class of electroactive polymers were precisely controlled after synthesis, a remarkable gas selectivity could be achieved. For PAni investigated in the presence of different gas pairs, selectivity values of 3590 for H2/N2, 30 for O2/N2, and 336 for CO2/CH4 were obtained [195]. It has also been demonstrated that other ECPs such as poly(dimethoxy-p-phenylenevinylene) were appropriate for gas separations [197]. 

Other ECP films incorporating unsubstituted heteropolyanions have been used for the electrocatalytic reduction of anions such as nitrite, bromate, and chlorate [149], However, for these systems no adduct was produced in the course of the electrocatalysis, and consequently, a lower selectivity was observed. 

Preuss, Stoll, and co-workers at Stuttgart have employed several other ECP methods, which include core polarization effects in molecular calculations. The ECPs for all of the elements in the periodic table including lanthanides and actinides have been generated by these authors. They have also used these ECPs for computing the spectroscopic constants and potential energy curves of lanthanide oxides such as GdO, EuO, YbO, etc. 

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